Field of the Invention
The present invention relates to a method of recording information in a phase-change optical recording medium, reproducing information therefrom, and rewriting information recorded in the phase-change optical recording medium.
The present invention also relates to an apparatus which is (capable of recording information in a phase-change optical recording medium, reproducing information therefrom, and rewriting information recorded in the phase-change optical recording medium by use of the above-mentioned method.
For improving the quality of recording signals in the phase-change recording, various recording compensation methods have been disclosed.
For example, Japanese Laid-Open Patent Application 63-266632 discloses, as an effective method for improving the quality of recording signals, a method of recording long amorphous marks by use of a pulse string in a PWM (pulse width modulation) recording, using a recording film having a high crystallization speed.
In Japanese Laid-Open Patent Application 63-266633 and U.S. Pat. No. 5,0150,351, a laser energy level of a pulse string is increased at a leading edge and a trailing edge of the pulse string, or the duration of irradiation is lengthened, whereby the jitters of the mark edge positions are controlled and the quality of recording signals is improved.
Furthermore, as disclosed in Japanese Patent Publication 63-29336, there is known a method of recording information signals in an optical disk by use of an optical disk recording apparatus by having a light spot of a laser team scan the optical disk as the optical disk is irradiated with the laser beam, and by subjecting the light spot of the laser beam to power modulation
There is also known a method for appropriately adjusting and setting the recording conditions such as light power for recording and the width of recording light pulse by reproducing information signals recorded in the optical disk, and monitoring the amplitude of the reproduced signal and the length of recording marks.
Furthermore, Japanese Laid-Open Patent Applications 9-138946, 9-138941, and 9-219021 disclose, as a method of improving the quality of recording signals, a method of recording and reproducing information in an information recording medium as shown in FIG. 1, wherein when information is recorded in the information recording medium by modulating an input signal and conducting pulse width modulation recording,
(A) a recording pulse string for recording and rewriting,
corresponding to a zero (0) signal with a signal width nT, in which n is a positive integer, and T is a clock unit time, after the modulation of the input signal, is a continuous electromagnetic wave with a power level e, and
(B) a recording pulse string for recording and rewriting, corresponding to a one (1) signal with a signal width nT, in which n is a positive integer, and T is a clock unit time, after the modulation of the input signal, is an electromagnetic wave pulse string having:
a front-pulse portion tp with a power level a and a pulse duration period x,
a multi-pulse portion mp comprising a low-level pulse with a power level b and a high-level pulse with a power level c, with a total pulse duration period T and a duty ratio y, alternately repeating (n-nxe2x80x2) times continuously, and
an off-pulse portion op with a power level d and a pulse duration period z, in which x, y and z respectively satisfy 0.5xe2x89xa6xxe2x89xa62.0T, 0.125xe2x89xa6yxe2x89xa60.0875, and 0.125Txe2x89xa6zxe2x89xa61.0T, nxe2x80x2 is a positive integer which satisfies the condition of nxe2x80x2xe2x89xa6n, and (a and c)xe2x89xa7exe2x89xa7(b and d)
These prior art references also disclose an apparatus for recording and reproducing information in an information recording medium by use of the above-mentioned method
The above-mentioned method, however, is not always suitable for improving the quality of recording signals in phase change recording when multi-speed recording or CAV (constant angular velocity) recording is carried out.
Recently, in a rewritable information recording medium, in particular, in the phase-change optical recording medium, there is a keen demand for a technology that makes it possible to record information at a plurality of different linear velocities in one information recording medium. Furthermore, high speed recording is in demand. As a matter of course, the CAV recording which is advantageous to the attainment of high speed recording is also in demand.
However, the technologies described in the above-mentioned prior art references, Japanese laid-Open Patent Applications 9-138946, 9-130947, and 9-219021, cannot meet the above mentioned demands. Specifically, for example, a recording strategy having fp, mp and op, which is capable of recording at a 4xc3x97 CD linear speed, cannot obtain sufficiently high signal quality at an 8xc3x97 speed recording and at a 10xc3x97 speed recording when multiple recording is conducted at the 8xc3x97 speed recording and the 10xc3x97 speed recording.
it is therefore a first object of the present invention to provide a method of recording and reproducing information for carrying out multi-speed recording and/or CAV (constant angular velocity) recording, which is capable of obtaining high signal quality, and attaining the improvement on the stability, reliability, and general-use properties.
A second object of the present invention is to provide an information recording and reproducing apparatus which is capable of conducting the above-mentioned method.
The first object of the present invention can be achieved by a method of recording and reproducing information in a phase-change optical recording medium comprising a recording layer which comprises a phase-changeable recording material capable of being subjected to a phase-change by irradiation of an electromagnetic wave for recording, reproducing and/or rewriting information, wherein when information is recorded in the phase change optical recording medium by modulating an input signal and conducting pulse width modulation recording,
(A) A recording pulse string for recording and rewriting,
corresponding to a zero (0) signal with a signal width nT, in which n is a positive integer, and T is a clock unit time, after the modulation of the input signal, is a continuous electromagnetic wave with a power level e, and
(B) a recording pulse string for recording and rewriting, corresponding to a one (1) signal with a signal width nT, in which n is a positive integer, and T is a clock unit time, after the modulation of the input signal, is an electromagnetic wave pulse string having:
a front-pulse portion tp with a power level a and a pulse duration period x,
a multi-pulse portion mp comprising a low-level pulse with a power level b and a high-level pulse with a power level c, with a total pulse duration period T and a duty ratio y, alternately repeating (n-nxe2x80x2) times continuously, and
an off-pulse portion mp with a power level d and a pulse duration period z, in which x, y and z respectively satisfy 0.5Txe2x89xa6xxe2x89xa62.0T, 0.125xe2x89xa6yxe2x89xa60.875, and 0.125Txe2x89xa6zxe2x89xa61.0T, nxe2x80x2 is a positive integer which satisfies the condition of nxe2x80x2xe2x89xa6n, and (a and c)xe2x89xa7exe2x89xa7(b and d), wherein the duty ratio y is decreased as a recording linear velocity for the phase-change optical recording medium is increased, whereby multi-speed recording or CAV (constant angular velocity) recording is carried out.
In the above-mentioned method, by decreasing the duty ratio y as a recording linear velocity for the phase-change optical recording medium is increased, recording energy is replenished during high speed recording, which facilitates the multi speed recording and the CAV (constant angular velocity) recording.
In the above-mentioned method, it is preferable that the recording linear velocity, when the duty ratio y is 0.5, be set in a range of more than (vH+VL)/2 to VH or less, that is, (VH+VL)/2 less than the recording linear velocity (when y=0.5)xe2x89xa6VH, wherein VH is a maximum recordable linear velocity and VL is a minimum recordable linear velocity, whereby recording signals with improved drive-media matching performance can be obtained.
The second object of the present invention can be achieved by an information recording and reproducing apparatus for recording and reproducing information by use of the above-mentioned method of recording and reproducing information.